Re: Improving connection scalability: GetSnapshotData() - Mailing list pgsql-hackers

From Robert Haas
Subject Re: Improving connection scalability: GetSnapshotData()
Date
Msg-id CA+TgmoaQSdoMDVMqgmXDng6n4NBv8e9-3Eb-f3r5y37gR5j9Yw@mail.gmail.com
Whole thread Raw
In response to Re: Improving connection scalability: GetSnapshotData()  (Andres Freund <andres@anarazel.de>)
Responses Re: Improving connection scalability: GetSnapshotData()  (Andres Freund <andres@anarazel.de>)
List pgsql-hackers
On Tue, Apr 7, 2020 at 1:51 PM Andres Freund <andres@anarazel.de> wrote:
> > ComputedHorizons seems like a fairly generic name. I think there's
> > some relationship between InvisibleToEveryoneState and
> > ComputedHorizons that should be brought out more clearly by the naming
> > and the comments.
>
> I don't like the naming of ComputedHorizons, ComputeTransactionHorizons
> much... But I find it hard to come up with something that's meaningfully
> better.

It would help to stick XID in there, like ComputedXIDHorizons. What I
find really baffling is that you seem to have two structures in the
same file that have essentially the same purpose, but the second one
(ComputedHorizons) has a lot more stuff in it. I can't understand why.

> What's the inconsistency? The dropped replication_ vs dropped FullXid
> postfix?

Yeah, just having the member names be randomly different between the
structs. Really harms greppability.

> > Generally, heap_prune_satisfies_vacuum looks pretty good. The
> > limited_oldest_committed naming is confusing, but the comments make it
> > a lot clearer.
>
> I didn't like _committed much either. But couldn't come up with
> something short. _relied_upon?

oldSnapshotLimitUsed or old_snapshot_limit_used, like currentCommandIdUsed?

> It's just adjusting for the changed name of latestCompletedXid to
> latestCompletedFullXid, as part of widening it to 64bits.  I'm not
> really a fan of adding that to the variable name, but surrounding code
> already did it (cf VariableCache->nextFullXid), so I thought I'd follow
> suit.

Oops, that was me misreading the diff. Sorry for the noise.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company



pgsql-hackers by date:

Previous
From: Robert Haas
Date:
Subject: Re: Improving connection scalability: GetSnapshotData()
Next
From: Andres Freund
Date:
Subject: Re: Improving connection scalability: GetSnapshotData()